Method and means for improving the operation of a steam gas plant including a gas turbine and a steam turbine with a steam generator at the downstream end

ABSTRACT

In a steam gas plant comprising a steam generator fed by the exhaust gases of a gas turbine and feeding a steam turbine, the condensed steam at the output of the steam turbine is returned to the input of the steam generator through water heaters and a deaerator. To ensure constancy of the temperature of the water in the deaerator, which should be lower than the saturation temperature of the steam heating said the deaerator even under reduced load conditions, a fraction of the water reaching or about to reach said the deaerator is returned to the condenser. A gate controlled by the temperature at the input of the deaerator is adapted to ensure constancy of the temperature of the water into the deaerator.

United States Patent Vidal et a1.

[72] Inventors: ,Iean Vidal, Ville dAvray; Jean Parlsot, Jacques Lemoine, Paris, all of France [73 Assignee: Stein Industrie, Paris, France [22] Filed: May 13, 1970 [21] Appl. No.: 36,815

US. Cl. ..60/39.18 B, 60/92, 60/ 107 Int. Cl ..F02c 7/02, F0lk 13/00 Field of Search ..60/95, 108, 105, 106, 107,

References Cited UNITED STATES PATENTS 11/1961 Pirsh "150/105 51 Sept. 19, 1972 Rudd ..60/ 105 Nettel ..60/95 X [5 7] ABSTRACT In a steam gas plant comprising a steam generator fed by the exhaust gases of a gas turbine and feeding a steam turbine, the condensed steam at the output of the steam turbine is returned to the input of the steam generator through water heaters and a deaerator. To ensure constancy of the temperature of the water in the deaerator, which should be lower than the saturation temperature of the steam heating said the deaerator even under reduced load conditions, a fraction of the water reaching or about to reach said the deaerator is returned to the condenser. A gate controlled by the temperature at the input of the deaerator is adapted to ensure constancy of the temperature of the water into the deaerator.

3 Claims, 1 Drawing Figure PATENTED SEP 1 9 1912 m mlllllklll LILIIL METHOD AND MEANS FOR IMPROVING THE OPERATION OF A STEAM GAS PLANT INCLUDING A GAS TURBINE AND A STEAM TURBINE WITH A STEAM GENERATOR AT THE DOWNSTREAM END Our invention has for its object a steam gas plant including a gas turbine, a steam turbine with its steam generator at the downstream end wherein the outputs of one or more gas turbines feed the burners of one or more steam generators while one or more steam turbines are associated with heat exchangers and a deaerator to heat the feed water of the steam generator;

Our invention has for an object a method for operating a plant of such a type, in particular to allowing proper operation of the whole plant under partial loads.

Our improved method consists in maintaining at a suitable predetermined value the temperature of the water at the input of the deaerator under partial loads while a fraction of the water reaching the deaerator is returned to the condenser.

Our invention also includes a plant for executing such a method in which the deaerator is connected with the condenser through a channel in which is inserted a regulating gate and means for controlling the gate to regulate the temperature of the water at the input of the deaerator. The regulating gate may be provided with a by-pass incorporating a cut-off valve.

We have described hereinafter by way of example and in a non-limiting sense an embodiment of our improved plant, reference being made to the single FIGURE of the accompanying drawing which forms a diagrammatic view of such a plant.

Our improved plant includes three gas turbines 1 fed with fuel at 2 and sending their exhaust gases into the burners of a steam generator 3 through the agency of three cut-off dampers 4. The exhaust gases which contain large amounts of oxygen ensure the combustion inside the steam generators of the fuel fed to it at 5.

The steam generator 3 is provided with a superheater 6, a reheater 7 and three ec'onomizers 8, 9, 10. The flue gases pass in succession through these different elements before they are exhausted into the chimney at 1 l.

The plant includes also a steam turbine constituted by two stages or groups of stages 12a, 12b. The input of the stage or group of stages 12a is connected with the output of the superheater 6 while its output is connected with the input of the reheater 7. The input of the second stage or group of stages 12b is connected with the output of the reheater 7. The output of the group of stages 12b of the steam turbine is connected with the input of a pump 13 through the agency of a condenser 14. At the outlet of the pump l4,-the condensed water is sent into a water heater 15 fed by steam passing out of an extraction port S1 of the turbine. The stream of water passing out of the heater is divided into two fractions of which one passes through the economizer while the other is sent into two water heaters 16 and 17 fed by steam tapped off the extraction ports S2 and S3 of the turbine respectively. At the output of the water heater 17, the water is mixed with the water passing out of the economizer 10 and the mixture is then sent into the deaerator l8 fed by the steam tapped off an extraction port S4 of the steam turbine.

The stream of water passing out of the deaerator 18 is sucked in by a feed pump 19 which is connected with the input of the steam generator 3 through a water heater 20 fed by the steam passing out of the extraction port S5 and the economizer 8, the economizer 9 being inserted in parallel with the water heater 20.

The deaerator 18 is connected with the condenser 14 through a discharge pipe 21 provided with a regulating 0 gate 22, said gate being controlled by the temperature of the water at the input of the deaerator as measured at 23. The regulating gate 22 is provided with a by-pass which contains cut-off gate 24 controlled by a remote station.

Lastly a main alternator 25 is connected with the shaft of the turbine 12a, 12b.

It is a well-known fact that in such a plant, the deaerator 18 operates under proper operative conditions provided the feed water is at a temperature lower than the saturation temperature corresponding to the pressure of the extracted steam feeding it. Furthermore, the plant is sufficiently efficient for intermediate loads only if the gas turbines I operate under full load and send into the steam generator the same throughput of exhaust gases as sent under full load conditions. Consequently, the throughput of flue gases passing through the economizer 10 remains substantially the same under partial loads and under full load and since the throughput of feed water is reduced with the load, the result is that the temperature of the water at the output of the economizer 10 increases when the load decreases.

In order to retain proper operation of the deaerator it is necessary to limit the rise in the temperature of the feedwater at the output of the economizer 10 and this may be accomplished by adjusting the division of the stream of water between the economizer l0 and heaters 16 and 17, but such an operation is limited by the capacity of the water heaters 16 and 17 and may be insufficient for certain low loads. This is the case of the present plant where the temperature of the water for such low loads at the input of the deaerator 18 is too high, even if the water heaters 16 and 17 are already cut off.

ln our invention, the temperature of the water at the output of the economizer 10 is reduced by increasing the throughput of water passing through the economizer 10 as provided by opening the regulating gate 22. The result is the reliable operation of the steam turbine under low intermediate loads without reducing the load on the gas turbine whereby the efficiency of the plant is increased for such low loads. The method according to our invention consists therefore in transferring only a fraction of the heat contained in the flue gases to the water flowing through the condenser.

Our invention also prevents damage to the plant in the case of disconnection of the steam generator where the heat applied to the economizer 10 by the hot gases passing out of the steam generator can cause untimely boiling in the economizer.

To this end a reduced basic circulation is maintained through the economizer 10 by opening the by-pass 24.

The preceding description shows that our improved method and means lead in particular to the following advantages:

it improves the general efficiency of the plant under partial loads while ensuring a suitable water temperature at the input of the deaerator as obtained by an increased throughput of water flowing through the economizer 10.

it improves the operation of the water feeding means in case of disconnection of the steam generator since it allows the heat applied to the economizer by the hot gases produced by the steam generator to be transferred to the condenser.

Obviously, our invention should not be considered as limited to the embodiment described and illustrated and in particular the discharge pipe 21 may be connected to the condenser 14 at any point of the channel connecting the deaerator with the output of the economizer 10 as well as to the deaerator. All modifi cations falling within the scope of the accompanying claims form part of the present invention.

What we claim is:

1. In the operation of a steam gas plant including at least one gas turbine, a steam generator with burners fed by the exhaust gases from said gas turbine, a steam turbine fed by said steam generator, a condenser at the output of said steam turbine, means heating the water passing out of said condenser and a deaerator through which the water is returned into the input of said steam generator, the steps consisting in returning to said condenser, a fraction of the water entering said deaerator and adjusting said fraction to vary the water flow through said water heating means at the output of said condenser in order to maintain the temperature of the water substantially constant at the input of said deaerator.

2. In a steam gas plant including at least one gas turbine, a steam generator with burners fed by the exhaust gases from said gas turbine, a steam turbine fed by said steam generator, a condenser at the output of said steam turbine, means heating the water passing out of said condenser and a deaerator through which the water is returned into the input of said steam generator, the provision of a connection adapted to return to said condenser a fraction of the water fed by the heating means into said deaerator and a gate in said connection controlled by the temperature at the input of said deaerator to vary the water flow through said water heating means at the output of said condenser in order to maintain said temperature substantially constant.

3. A steam gas plant as claimed in claim 2 comprising a by-pass across said gate and a second gate within said by-pass adapted to cut off said by-pass.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3:691:76O Dated Se tember 19, 1972 Inventor(s) Jean Vidal, Jean Parisot, and Jacques Lemoine It is certified that error appears in the aboveidentified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet before insert;

Foreign Application Priority Data May 14, 1969 France...'...69 14159-- Signed and sealed this 20th day of February 1973.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents F ORM PO-105O (10-69) USCOMM-DC 60376-P59 b U,S GOVERNMENT PRINTING OFFICE: I969 0-365-334 

1. In the operation of a steam gas plant including at least one gas turbine, a steam generator with burners fed by the exhaust gases from said gas turbine, a steam turbine fed by said steam generator, a condenser at the output of said steam turbine, means heating the water passing out of said condenser and a deaerator through which the water is returned into the input of said steam generator, the steps consisting in returning to said condenser, a fraction of the water entering said deaerator and adjusting said fraction to vary the water flow through said water heating means at the output of said condenser in order to maintain the temperature of the water substantially constant at the input of said deaerator.
 2. In a steam gas plant including at least one gas turbine, a steam generator with burners fed by the exhaust gases from said gas turbine, a steam turbine fed by said steam generator, a condenser at the output of said steam turbine, means heating the water passing out of said condenser and a deaerator through which the water is returned into the input of said steam generator, the provision of a connection adapted to return to said condenser a fraction of the water fed by the heating means into said deaerator and a gate in said connection controlled by the temperature at the input of said deaerator to vary the water flow through said water heating means at the output of said condenser in order to maintain said temperature substantially constant.
 3. A steam gas plant as claimed in claim 2 comprising a by-pass across said gate and a second gate within said by-pass adapted to cut off said by-pass. 